| Ageratina macvaughii R.M. King & H. Rob., 1978 |
| Ageratina mairetiana (DC.) R.M. King & H. Rob., 1970 |
| Ageratina mairetiana var. elucens (McVaugh) B.L. Turner, 1987 |
| Ageratina mairetiana var. mairetiana (DC.) R.M. King & H. Rob., 1970 |
| Ageratina malacolepis (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina manantlana B.L. Turner, 1988 |
| Ageratina mariarum (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina markporteri B.L. Turner, 2012 |
| Ageratina mayajana B.L. Turner, 2006 |
| Ageratina mazatecana B.L. Turner, 2006 |
| Ageratina megacephala B.L. Turner, 2010 |
| Ageratina megaphylla B.L. Turner, 2013 |
| Ageratina miahuatlana B.L. Turner, 1995 |
| Ageratina microcephala B.L. Turner, 2012 |
| Ageratina miquihuana (B.L. Turner) R.M. King & H. Rob., 1977 |
| Ageratina modesta (Kunth) R.M. King & H. Rob., 1972 |
| Ageratina moorei B.L. Turner, 1990 |
| Ageratina motozintlensis R.M. King & H. Rob., 1990 |
| Ageratina muelleri (Sch. Bip. ex Klatt) R.M. King & H. Rob., 1970 |
| Ageratina multiserrata (Sch. Bip.) R.M. King & H. Rob., 1972 |